Sulawesi, Indonesia

Main commodities: Au
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The Mesel sediment hosted disseminated gold deposit is located in the Ratatotok district of North Sulawesi, Indonesia, ~70 km SSW of the city of Manado, and within 5 km of the SE coast of the peninsular that forms NW Sulawesi (#Location: 0° 53' 19"N, 124° 39' 44"E).

The Mesel deposit was discovered by Newmont geologists in 1988 and comprised a mineable reserve of 7.8 Mt @ 7.3 g/t Au using a 2 g/t Au cutoff.

The deposit occurs in a structurally complex zone within the North Sulawesi magmatic arc. The predominant lithologies are a carbonate siliciclastic succession deposited in an extensional middle Miocene basin. In the vicinity of the mine, the sediments are intruded by sills, dykes and laccoliths of hornblende-plagioclase phyric andesite.

The distribution of hydrothermal alteration is controlled by two steeply dipping major faults, and intersecting shallowly dipping lithologies. Gold bearing carbonate rocks have characteristically undergone decalcification, dolomitisation and silicification, with ubiquitous brecciation textures. The breccias are due to sedimentary, tectonic and hydrothermal dissolution processes. Insoluble residues (clay and organic matter) and pyrite line stylolites and breccia clasts in alteration zones, while clay is present in some rock types.

The gangue mineralogy includes quartz, chalcedony, calcite and dolomite. Sulphides such as pyrite, realgar, orpiment, stibnite and cinnabar accompany the gangue and precious metals. Trace elements Ag, As, Sb and Hg are zoned through the deposit, with Ag coinciding with high grade gold and silica, while As, Sb and Hg are found on the peripheries.

Gold prefers carbonate lithologies adjacent to and beneath the andesite intrusives. Gold is mid to late stage in the paragenesis and sub-micron in size, locked in very fine (<10 µm) disseminated and fracture controlled arsenical pyrite. Three major ore types are recognised, namely silica-pyrite, carbonate-pyrite and oxide.

The orebody has a central, near vertical, high grade feeder system, flanked by tabular, shallowly inward dipping, moderate grade zones. The 100 gm-m contour outlines a 600 x 250 m zone in plan, with gold extending to a depth of 150 m.

See the references below for more detail.

The most recent source geological information used to prepare this summary was dated: 1999.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
   Selected References:
Garwin S L, Hendri D, Lauricella P F  1995 - The geology of the Mesel sediment hosted gold deposit, North Sulawesi, Indonesia: in Mauk J L, St George J D (Eds.),  Exploring the Rim Proceedings of the1995 PACRIM Cong., Auckland, New Zealand, 19-22 November 1995    pp 221-226
Hendri D, Farmer M C  1997 - The discovery of the Mesel sediment hosted gold deposit, North Sulawesi, Indonesia: in   New Generation Gold Mines 99, Case Histories of Discovery, Conf. Proc., Perth, 24-25 Nov, 1997 AMF, Adelaide    pp 5.1-5.13
van Leeuwen, T.M. and Pieters, P.E.,  2011 - Mineral Deposits of Sulawesi: in   The Sulawesi Mineral Resources 2011 Seminar, 28‐29 November 2011, Manado, North Sulawesi, Indonesia, Masyarakat Geologi Ekonomi Indonesia - Indonesian Geologists Association (MGEI‐IAGI), Jakarta    Proceedings, 130p.

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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